1. Field of the Invention
The present invention relates to an ignition device for an internal combustion engine to be mounted on various kinds of vehicles.
2. Description of the Related Art
JP-A-8-135547 or its counterpart U.S. patent, U.S. Pat. No. 5,603,308A, discloses an ignition device for an internal combustion engine that has a constant primary current control circuit. The disclosed ignition device has a network composed of a plurality of resistors to detect a potential. The potential is compared with a reference level for a feed-back control to provide a suitable gate voltage to be applied to the gate of a primary current control transistor. Although the disclosed ignition device is effective to prevent abnormal oscillation of the constant primary current control circuit, it may not provide an accurate fail signal when it fails because the fail signal is formed from the gate voltage, which may sometimes fluctuate when a power source voltage fluctuate or become to low to detect.